Radio communication is becoming increasingly widespread and used for a variety of communication purposes. As a result, the demand for radio frequency spectrum is likewise increasing. The concept of secondary-use radio systems has recently been proposed as a way of addressing radio spectrum demand. Secondary-use systems operate in the unused channels or spectrum portions of spectrum regions reserved for primary operators. Primary operators, or incumbents, are generally licensed to use a spectrum portion, such as a channel, and include entities such as television, commercial radio broadcasters, auxiliary broadcasting services (e.g. wireless microphones), radio-telephone operators, and land-mobile radio systems. Secondary use of spectrum is generally achieved though the use of cognitive radio techniques, which allow a radio unit to self-configure its operating parameter list to adapt to the ambient radio environment. Geo-location databases may be utilized to obtain information about the ambient radio environment, based on the location of the requesting radio unit or spectrum user. For example, in the United States, the geo-location databases can be queried in order to obtain channel availability information for secondary usage of the broadcast television spectrum, for example.
In a given geographic region, the spectrum region reserved for television broadcast will have a number of unused channels which may be made available to secondary use operators under appropriate conditions. For example, present proposals for secondary-use operation require a secondary-use operator to periodically update channel information used by the secondary-use operator to allocate radio resources. The channel information includes parameters such as which broadcast channels are occupied by primary operators (broadcasters), the allowed transmit power on unoccupied channels, and so on. To facilitate updating the channel information record used by a secondary operator, a database is maintained which correlates geographic location with channel usage of primary operators, as well as the other relevant channel parameters. The secondary-use operator may then query the database by providing the geographic location of the secondary-use operator's transmitter, and the database will provide channel information for that location in response which the secondary operator maintains as a radio operating parameter list or channel information record. A problem arises, however, when the secondary-use operator is unable to connect to the database, such as upon the occurrence of a network fault. Secondary-use may be regulated such that the secondary-use operator is required to refresh its channel information before commencing further communication activity. Therefore, there is a need for a way to keep channel information up to date despite potential fault conditions.